1. Field of the Invention
The present invention is a coating and developing apparatus, and a coating and developing method for coating a resist liquid on a surface of a substrate and developing the substrate after a dipping exposure process.
2. Background Art
A method for forming a resist pattern on a substrate, such as a glass substrate for use in a semiconductor wafer (hereinafter referred to as a “wafers”) or LCD (Liquid Crystal Display) is carried out in a system composed by connecting a coating and developing apparatus comprising a coating section for coating a resist liquid on a substrate and a developing section for developing the substrate after exposure with an exposing apparatus.
In an exposing technique of an exposing apparatus, in order to enhance resolution by improving the exposing technique employing an existing light source, for example, argon fluoride (ArF) or krypton fluoride (KrF), there is a method of exposing a surface of a substrate with an optically transparent liquid layer being formed thereon (hereinafter, this method is referred to as a “dipping exposure method”). An exposing apparatus for performing such a dipping exposure process is explained briefly with reference to FIG. 11. Above a wafer W held horizontally by a holding mechanism (not shown), an exposing means 1 is arranged to face a surface of the wafer W with a gap. At a central distal portion of the exposing means 1, a lens 10 is provided. At the outer periphery of the lens 10, a feeding port 11 for feeding a solution, for example, pure water for forming a liquid layer on the surface of wafer W, and an aspirating port 12 for aspirating and collecting pure water fed to the wafer W are provided, respectively. In this case, by feeding pure water onto the surface of wafer W from the feeding port 11 while collecting the pure water by using the aspirating port 12, a liquid layer (pure water layer) is formed between the lens 10 and the surface of wafer W. Thereafter, light is emitted from a light source (not shown), passes through the lens 10, and is transmitted through the liquid layer and radiated onto the wafer W. In this way, a predetermined circuit pattern is transferred to the resist coated on the wafer W.
Subsequently, for example, as shown in FIG. 12, while the liquid layer is formed between the lens 10 and the surface of the wafer W, an exposing means 1 is driven to slide laterally such that the exposing means 1 is located at a position corresponding to a next transfer region (shot region) 13. Then, by repeating the operation to irradiate the wafer W with light, predetermined circuit patterns are successively transferred to the resist on the surface of the wafer W. It is noted that the shot region 13 is depicted in a larger than actual size.
Before performing a dipping exposure process after the resist liquid is coated on the wafer, in order to control elution of the resist and render water drops generated upon the dipping exposure process difficult to remain on the wafer surface, formation of a water-repellent protective film on the surface of the wafer has been studied (Patent Document 1).
However, the wafer is often transferred from the exposing apparatus to the coating and developing apparatus while water drops still remain on the wafer. In such a case, when heating is provided to the wafer W after exposure, if water drops exist on the wafer, the temperature at sites on which the water drops remain becomes different from other regions, leading to causing an adverse effect on the pattern resolution just below such sites. Therefore, it is necessary to wash the surface of the wafer after exposure to remove water drops.
To address this problem, provision of a washing apparatus to the coating and developing apparatus has been studied. After attaching onto a wafer W, water drops gradually become small in size with time, and the size becomes smaller quite rapidly at a certain point of time. When the timing of washing the wafer is later than the point of time the size of water drops become smaller quite rapidly, the water drops will soak into the protective film and reach the surface of the resist film, thus forming layers insoluble to a developing liquid or the so-called water marks. In such a case, uniformity of the line width of the circuit pattern will be adversely affected.
Generally, in order to avoid generation of particles, a peripheral portion of a wafer is first exposed in a periphery exposing section for the wafer before subjected to a primary exposure process, and a resist portion at the periphery of the wafer is then removed when a developing liquid is supplied. However, since the protective film tends to be damaged upon the periphery exposing process, it has been examined to perform the periphery exposing process after a wafer to be processed is returned from the exposing apparatus to the coating and developing apparatus.
Meanwhile, for a resist of a chemically amplified type, in order to control the degree of diffusion of an acid to be produced upon exposure, it is preferred to adjust the time (PED time) to be taken from a point of time a wafer is exposed to a point of time of starting a heating process. In the case of using a heating section in which a heating plate and a cooling plate which also serves as an exclusive arm for a wafer are incorporated, for example, it is attempted to make the PED time constant by placing a wafer on the cooling plate so as to adjust the waiting time (Patent Document 2).
However, in the method of performing the adjustment of the PED time by using the cooling plate, the number of heating sections becomes large, leading to increase of the cost. To address this issue, if attempting to provide a waiting section such that a wafer can be transferred from the waiting section to a heating section after the adjustment of the PED time has been provided to the wafer in the waiting section, significant variation of the time from carrying-in to carrying-out of the wafer at the washing section or periphery exposing section occurs due to operating properties of a wafer carrying arm, thus increasing the range of adjusting time in the waiting section. In particular, since the number of modules in which each wafer is carried is increased by one due to the provision of the washing section, the control program for the wafer carrying arm should take much time to be well devised in order to ensure a desirably high throughput. On the other hand, if the difference of timings to carry each wafer out of the waiting section is too large, the control of the wafer carrying arm becomes significantly difficult (of course, this problem will not occur if the throughput is disregarded).    Patent Document 1: TOKUKAI No. 2005-175079, KOHO    Patent Document 2: TOKUKAI No. 2004-193597, KOHO